If you got a new job about a month ago and didn't like it and knew a different job wouldn't be hard to find, would you leave the job you didn't like?

How long would you give yourself to decide if it's worth staying or leaving?

I'm really unsure if I like my new job and while I want the experience, I'm terrified of developing bad habits in my career and going against everything I've ever learned in school. I want to bail so bad, but also want to model the change I know is necessary. I'm stumped!